var md5 = new iot.crypto.MD5();
md5.update(iot.stringToUintArray('hello'))
var md5str = md5.final()
assert(md5str == '5d41402abc4b2a76b9719d911017c592','md5str == 5d41402abc4b2a76b9719d911017c592 but '+md5str);
md5.reset();
md5.update(iot.stringToUintArray('helloworld'))
md5str = md5.final()
assert(md5str == 'fc5e038d38a57032085441e7fe7010b0','md5str == fc5e038d38a57032085441e7fe7010b0 but '+md5str);
